To assess feasibility of conical k-space trajectory free-breathing UTE chest MRI versus 4D flow and effects of 50% data subsampling and soft-gated motion correction, 32 consecutive children were recruited. Images scored by two blinded radiologists showed good to excellent delineation of all evaluated structures. UTE surpassed 4D flow for lungs and airways and was equivalent for pulmonary arteries. 50% subsampling mildly reduced but maintained diagnostic image quality, favoring its shorter scan time. Soft-gating slightly improved pulmonary artery delineation for one reader but overall degraded images, possibly due to noise from data subsampling, and suggesting motion-robustness of the conical golden-ordered trajectory.